Hollow optical fiber unit for optical fiber sensor with hexagonal head and threaded shaft

Abstract

An optical fiber unit enables secure grasping of an optical fiber sensor via a jig while avoiding damage to an optical fiber cable. The optical fiber unit for the optical fiber sensor includes an optical fiber cable, a shaft, and a head. The shaft includes a peripheral surface having a male thread, and a through-hole for an inserted optical fiber cable. The head is shaped in a hexagonal prism including six sides and a bottom. The shaft is connected to the bottom of the head. The optical fiber cable extends the head, and extends out of the head in a direction substantially parallel to two parallel sides of the six sides from at least one of the six sides excluding the two parallel sides.

The invention claimed is: 
     
       1. An optical fiber unit for an optical fiber sensor, the optical fiber unit comprising:
 a head shaped as a hexagonal prism including six sides and a bottom; 
 an optical fiber cable extending inside the head, and extending out of the head in a direction substantially parallel to two parallel sides of the six sides from at least one of the six sides excluding the two parallel sides; and 
 a shaft connected to the bottom of the head, the shaft including a peripheral surface having a male thread, and a through-hole in which the optical fiber cable is inserted. 
 
     
     
       2. The optical fiber unit for an optical fiber sensor according to  claim 1 , wherein
 the head includes a space through which the optical fiber cable is placed, and the space communicates with the through-hole, and 
 the space forms an opening in the at least one of the sides excluding the two parallel sides, the opening having a width substantially equal to a diameter of the optical fiber cable, to thereby maintain the optical fiber cable in the direction extending substantially parallel to the two parallel sides of the six sides. 
 
     
     
       3. The optical fiber unit for an optical fiber sensor according to  claim 1 , wherein
 the optical fiber cable extends out of the head from a first side that is one of the six sides excluding the two parallel sides and a second side that is adjacent to the first side and is another one of the six sides excluding the two parallel sides by extending through a corner between the first side and the second side. 
 
     
     
       4. The optical fiber unit for an optical fiber sensor according to  claim 1 , wherein
 the opening is exposed across at least two sides including the first side and the second side. 
 
     
     
       5. The optical fiber unit for an optical fiber sensor according to  claim 1 , wherein
 the bottom of the head includes a tapered portion that communicates with the through-hole of the shaft. 
 
     
     
       6. The optical fiber unit for an optical fiber sensor according to  claim 1 , the optical fiber unit further comprising:
 a cover attached to the head to cover the space in a direction of a central axis of the through-hole. 
 
     
     
       7. The optical fiber unit for an optical fiber sensor according to  claim 1 , wherein
 the shaft includes a lens that is in contact with a tip of the optical fiber cable. 
 
     
     
       8. The optical fiber unit for an optical fiber sensor according to  claim 1 , the optical fiber unit further comprising:
 a nut that is screwed with the male thread of the shaft. 
 
     
     
       9. The optical fiber unit for an optical fiber sensor according to  claim 1 , wherein
 the optical fiber cable comprises a single cable. 
 
     
     
       10. The optical fiber unit for an optical fiber sensor according to  claim 1 , wherein
 the optical fiber cable comprises a first cable and a second cable. 
 
     
     
       11. The optical fiber unit for an optical fiber sensor according to  claim 1 , wherein the at least one of the six sides excluding the two parallel sides from which the optical fiber cable extends out from the head corresponds to a side of the head that is contiguous with one of the two parallel sides and that is not contiguous with the other of the two parallel sides.